Download or read book Entomologisk Tidskrift written by and published by . This book was released on 1907 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Collected Papers written by Peter Esben-Petersen and published by . This book was released on 1965 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Report on the Scientific Results of the Voyage of H M S Challenger During the Years 1873 76 Under the Command of Captain George S Nares and the Late Captain Frank Tourle Thomson R N written by Great Britain. Challenger Office and published by . This book was released on 1888 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Blind Massive MIMO Base Stations written by Marcus Karlsson and published by Linköping University Electronic Press. This book was released on 2018-08-15 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: Massive MIMO (Multiple-Input--Multiple-Output) is a cellular-network technology in which the base station is equipped with a large number of antennas and aims to serve several different users simultaneously, on the same frequency resource through spatial multiplexing. This is made possible by employing efficient beamforming, based on channel estimates acquired from uplink reference signals, where the base station can transmit the signals in such a way that they add up constructively at the users and destructively elsewhere. The multiplexing together with the array gain from the beamforming can increase the spectral efficiency over contemporary systems. One challenge of practical importance is how to transmit data in the downlink when no channel state information is available. When a user initially joins the network, prior to transmitting uplink reference signals that enable beamforming, it needs system information---instructions on how to properly function within the network. It is transmission of system information that is the main focus of this thesis. In particular, the thesis analyzes how the reliability of the transmission of system information depends on the available amount of diversity. It is shown how downlink reference signals, space-time block codes, and power allocation can be used to improve the reliability of this transmission. In order to estimate the uplink and downlink channels from uplink reference signals, which is imperative to ensure scalability in the number of base station antennas, massive MIMO relies on channel reciprocity. This thesis shows that the principles of channel reciprocity can also be exploited by a jammer, a malicious transmitter, aiming to disrupt legitimate communication between two single-antenna devices. A heuristic scheme is proposed in which the jammer estimates the channel to a target device blindly, without any knowledge of the transmitted legitimate signals, and subsequently beamforms noise towards the target. Under the same power constraint, the proposed jammer can disrupt the legitimate link more effectively than a conventional omnidirectional jammer in many cases. Massiv MIMO (eng: Multiple-Input--Multiple-Output) är en teknologi inom cellulär kommunikation som förutspås ha en betydande roll i framtida kommunikationssystem på grund av de många fördelar som denna teknologi medför. Massiv MIMO innebär att basstationen har ett stort antal antenner där varje antenn kan styras individuellt. De många antennerna gör att basstationen kan rikta de elektromagnetiska signalerna på ett sådant sätt att de förstärks på positioner där användarna befinner sig men släcks ut i övrigt. Detta i sin tur innebär att flera användare kan betjänas samtidigt, på samma frekvensband utan att de stör varandra. Detta medför att massiv MIMO kan erbjuda en högre datatakt än nutida cellulära kommunikationssystem. För att kunna rikta signalerna på ett effektivt sätt måste basstationen känna till kanalen, eller utbredningsmiljön, mellan sig själv och de användare som betjänas. När en användare precis kommer in i systemet vet basstationen inte var användaren befinner sig, men måste likväl tillgodose användaren med information om hur systemet fungerar. Nu måste alltså basstationen kommunicera med användaren, utan möjligheten att kunna rikta signalen på ett effektivt sätt. Det är detta problem som vi i huvudsak studerar i denna avhandling: hur man kan utnyttja de många antennerna på basstationen för att skicka information till användarna utan någon kanalkännedom. Vi studerar även hur en gruppantenn med många antenner, baserad på samma teknologi som massiv MIMO, kan användas som en störsändare. Störsändarens mål är att hindra kommunikationen mellan två enheter på ett effektivt sätt. En störsändare med ett stort antal antenner kan, utan någon kännedom av vad de två enheterna skickar, i många fall prestera bättre än en konventionell störsändare på grund av att störsignalen kan riktas mot en specifik enhet.

Download or read book Signal Processing Aspects of Cell Free Massive MIMO written by Giovanni Interdonato and published by Linköping University Electronic Press. This book was released on 2019-03-20 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fifth generation of mobile communication systems (5G) promises unprecedented levels of connectivity and quality of service (QoS) to satisfy the incessant growth in the number of mobile smart devices and the huge increase in data demand. One of the primary ways 5G network technology will be accomplished is through network densification, namely increasing the number of antennas per site and deploying smaller and smaller cells. Massive MIMO, where MIMO stands for multiple-input multiple-output, is widely expected to be a key enabler of 5G. This technology leverages an aggressive spatial multiplexing, from using a large number of transmitting/receiving antennas, to multiply the capacity of a wireless channel. A massive MIMO base station (BS) is equipped with a large number of antennas, much larger than the number of active users. The users are coherently served by all the antennas, in the same time-frequency resources but separated in the spatial domain by receiving very directive signals. By supporting such a highly spatially-focused transmission (precoding), massive MIMO provides higher spectral and energy efficiency, and reduces the inter-cell interference compared to existing mobile systems. The inter-cell interference is however becoming the major bottleneck as we densify the networks. It cannot be removed as long as we rely on a network-centric implementation, since the inter-cell interference concept is inherent to the cellular paradigm. Cell-free massive MIMO refers to a massive MIMO system where the BS antennas, herein referred to as access points (APs), are geographically spread out. The APs are connected, through a fronthaul network, to a central processing unit (CPU) which is responsible for coordinating the coherent joint transmission. Such a distributed architecture provides additional macro-diversity, and the co-processing at multiple APs entirely suppresses the inter-cell interference. Each user is surrounded by serving APs and experiences no cell boundaries. This user-centric approach, combined with the system scalability that characterizes the massive MIMO design, constitutes a paradigm shift compared to the conventional centralized and distributed wireless communication systems. On the other hand, such a distributed system requires higher capacity of back/front-haul connections, and the signal co-processing increases the signaling overhead. In this thesis, we focus on some signal processing aspects of cell-free massive MIMO. More specifically, we firstly investigate if the downlink channel estimation, via downlink pilots, brings gains to cell-free massive MIMO or the statistical channel state information (CSI) knowledge at the users is enough to reliably perform data decoding, as in conventional co-located massive MIMO. Allocating downlink pilots is costly resource-wise, thus we also propose resource saving-oriented strategies for downlink pilot assignment. Secondly, we study further fully distributed and scalable precoding schemes in order to outperform cell-free massive MIMO in its canonical form, which consists in single-antenna APs implementing conjugate beamforming (also known as maximum ratio transmission).

Download or read book Acta Societatis Pro Fauna Et Flora Fennica written by Societas pro Fauna et Flora Fennica and published by . This book was released on 1899 with total page 838 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vol. 68 is "Index generum et specierum quae operibus a Societate pro Fauna et Flora Fennica separatim editis continentur."

Download or read book Nationalmuseets skrifter written by and published by . This book was released on 1943 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aphid Reprints written by and published by . This book was released on 1935 with total page 1184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Pamphlets on Biology written by and published by . This book was released on with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handlingar written by and published by . This book was released on 1932 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Entomologiske meddelelser written by and published by . This book was released on 1910 with total page 898 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Videnskabelige meddelelser fra Dansk naturhistorisk forening i K benhaven written by Dansk naturhistorisk forening and published by . This book was released on 1919 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book South Syd America NO2 written by Torkel Karlberg and published by BoD - Books on Demand. This book was released on 2023-03-17 with total page 686 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Swedish and English. Information / Basic information. From year 2020. Book no 2. Sammanfattande resebeskrivning från dagboksanteckningar. Summary travel description from diary entries. Inledningsvis per kapitel på svenska och därefter på engelska. It starts in all chapters in Swedish and thereafter ends up in English. Endast ett urval/antal av alla foton kan vara med! Kontakta mig om du vill ha fler av korten! Just a special selection/number of all photos can be shown! Contact me if you want more photos! Grundidé och huvudsyfte: Att få uppleva Patagonien och Parque Nacional Iguaçu/ Iguassufallen samt att återigen uppleva nya delar av världens längsta bergskedja Anderna. Via: - start Argentina. Söderut till prioriterade Patagonien/Argentina. - Patagonien i Chile och södra Chile med Anderna. - Anderna i Argentina och västra Argentina. - Brazil västra och södra delar med Iguaçu, Ouro Preto, Rio de Janeiro, Florianopolis. - Uruguay, Rio de la Plata och avslut i Buenos Aires. In English. Basic idea and main purpose: To experience Patagonia and Parque Nacional Iguaçu / the Iguassu falls plus experience new parts of the world's longest mountain range the Andes. Via: - start Argentina. South to prioritized Patagonia/Argentina. - Patagonia in Chile and southern Chile with the Andes. - The Andes in Argentina and western Argentina. - Brazil western/southern parts including Iguaçu, Ouro Preto, Rio de Janeiro, Florianopolis. - Uruguay, Rio de la Plata and finish in Buenos Aires.

Download or read book Skrifter written by Kongelige Danske videnskabernes selskab and published by . This book was released on 1918 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Det Kongelige Danske videnskabernes selskabs skrifter written by and published by . This book was released on 1918 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Kongl Svenska vetenskaps akademiens handlingar written by and published by . This book was released on 1873 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Pamphlets on Biology written by and published by . This book was released on 1917 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: